cpuset: rename cpuset_node_allowed to cpuset_current_node_allowed

cpuset: rename cpuset_node_allowed to cpuset_current_node_allowed

Patch series "vmscan: enforce mems_effective during demotion", v5.

Change reclaim to respect cpuset.mems_effective during demotion when
possible.  Presently, reclaim explicitly ignores cpuset.mems_effective
when demoting, which may cause the cpuset settings to violated.

Implement cpuset_node_allowed() to check the cpuset.mems_effective
associated wih the mem_cgroup of the lruvec being scanned.  This only
applies to cgroup/cpuset v2, as cpuset exists in a different hierarchy
than mem_cgroup in v1.

This requires renaming the existing cpuset_node_allowed() to be
cpuset_current_now_allowed() - which is more descriptive anyway - to
implement the new cpuset_node_allowed() which takes a target cgroup.

This patch (of 2):

Rename cpuset_node_allowed to reflect that the function checks the current
task's cpuset.mems.  This allows us to make a new cpuset_node_allowed
function that checks a target cgroup's cpuset.mems.

Link: https://lkml.kernel.org/r/20250424202806.52632-1-gourry@gourry.net
Link: https://lkml.kernel.org/r/20250424202806.52632-2-gourry@gourry.net
Signed-off-by: Gregory Price <gourry@gourry.net>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>